1. The Field of the Invention
The present invention relates generally to wavelength division multiplexing (“WDM”) passive optical network (“PON”) systems. More particularly, embodiments of the invention relate to WDM PON systems using Fabry-Perot (“FP”) lasers seeded by continuous wave (“CW”) light from a central office to obtain single-mode operation and extend link distance.
2. The Relevant Technology
A passive optical network is a fiber-to-the-premises network architecture in which one or more passive optical devices are used to enable point to multipoint topologies. A PON configuration reduces the amount of fiber and central office equipment required compared with point-to-point architectures.
A typical WDM PON has a subscriber network architecture that forms a tree-type distribution topology. A central office is coupled over one fiber to a remote node for dividing a downstream optical signal received from the central office into multiple signals. The remote node than transmits the multiples signals to the respective subscriber units over independent fibers. Multiple upstream optical signals from the subscriber units are combined by the remote node before being transmitted to the central office over a single upstream fiber.
WDM PON systems offer the potential of large capacity, network security, and upgradability. However, these networks require low-cost optical signal sources at the central office and/or subscriber units. One conventional optical signal source implemented in WDM PON systems is the FP laser. The FP laser has a simple structure and is uncomplicated in operation, offering a significant cost advantage over other optical signal sources. However, multi-mode oscillation limits the transmission distance of FP lasers to less than 5 kilometers. As a result, low-cost FP lasers are unsuitable for emerging WDM PON systems requiring 10 Gigabit per second (“Gb/s”) data rates and signal transmission over 10 to 20 kilometers.
The subject matter claimed herein is not limited to embodiments that solve any disadvantages or that operate only in environments such as those described above. Rather, this background is only provided to illustrate one exemplary technology area where some embodiments described herein may be practiced